Although numerous clinical observational studies have been conducted over a period of over 30 years, the clinical significance of $Ureaplasma$ infection is still under debate. The $Ureaplasma$ speices. is a commensal in the female genital tract and considered to have of low virulence; however, $Ureaplasma$ colonization has been associated with infertility, stillbirth, preterm delivery, histologic chorioamnionitis, and neonatal morbidities, including congenital pneumonia, meningitis, bronchopulmonary dysplasia, and perinatal death. Recently, $Ureaplasma$ was subdivided into 2 separate species and 14 serovars. $Ureaplasma$ $parvum$ is known as biovar 1 and contains serovars 1, 3, 6, and 14, and $Ureaplasma$ $urealyticum$ (biovar 2) contains the remaining serovars (2, 4, 5, and 7-13). The existence of differences in pathogenicities of these 14 serovars and 2 biovars is controversial. Although macrolides are the only antimicrobial agents currently available for use in neonatal ureaplasmal infections, in the current clinical field, it is difficult to make decisions regarding which antibiotics should be used. Future investigations involving large, multicenter, randomized, controlled studies are needed before proper recommendations can be made for clinical practice.